Keyboard operated translating circuit



Sept. 9, 1952 W. H. BURKHART ET AL.

KEYBGARD OPERATED TRANSLATING CIRCUIT Filed April e, 1951 fsw? Patented Sept. 9, 1952 KEYBOARD OPERATED TRANSLATING CIRCUIT William Henry Burkhart, East Orange, and

Howard M. Fleming, Jr., Orange, N. J., assignors to Monroe Calculating Machine Company, Orange, N. J., a corporation of Delaware Application April 6, 1951, Serial No. 219,622

4 Claims.

This invention relates to electronic computers and more particularly to a keyboard operated translating circuit. l

In known computing machines, digital amounts in the coded decimal or 1, 2, 4, 8 system of binary notation, are represented by differentially timed pulses transmitted over four feed lines. This arrangement, while satisfactory for some applications, is found lacking in others wherein it is desired that coded digital information be transmitted over a single feed line.

The principal object of the invention, therefore, is the provision of a keyboard operated translating circuit with which the plural line, differentially timed pulse representation of digital information is transformed into a timed pulse code for single line transmission.

According to the invention a plurality of input lines along which differentially timed pulses are transmitted in accordance with a rst code, are selectively connected through rectiers and digital keyboard keys with a single output line along which timed pulses are to be fed in accordance with a second code. The output line is normally at a low potential, but when a digit key is depressed, the timed pulses from the input line or lines associated with the key, momentarily raise the potential of the output line to effect the transmission of timed pulses thereon.

A further development of the invention also includes means for initiating the generation of a predetermined number of pulses in accordance with the first code at each operation of a keyboard key in order to limit the number of digit signals that are transmitted in the second code; and means for eliminating the undesirable effects of key chatter on the operation of the associated circuitry.

Other objects and features of the invention will become apparent from the following description when read in the light of the attached drawings of which:

Fig. 1 is a circuit diagram illustrating the translator of the invention.

Fig. 2 is a diagram illustrating the arrangement of the input pulses for the circuit of Fig. 1.

Fig. 3 is a diagram illustrating the output of the circuit of Fig. 1 on the closure of the key switch for the digit five.

Fig. 4 is a circuit diagram illustrating the developed form of the invention.

Fig. 5 is a diagram illustrating the arrangement of the input pulses for the circuit of Fig. 4, and,

Fig. 6 is a diagram illustrating the output of 2 the circuit of Fig. 4 on the closure of the key switch for the digit five.

Referring to Fig. 1, the illustrated instance of the translator of the invention comprises four input lines bl, b2, b4, and ba over which differentially timed positive pulses are transmitted by any suitable means. Preferably, lines bl, b2, b4 and D18 are normally at a potential of 20 volts and are raised to 0 volts by said pulses. As shown in Fig. 2, the pulses are transmitted along lines bl, b2, b4 and D8 during successive time periods of which the first is allotted to line b l the second to line b2, etc. The pulse succession may be reinitiated or recycled after every fourth time period as shown in Fig. 2 or may be recycled only after a predetermined larger number of time periods as indicated in Fig. 5. This latter arrangement will be more fully described hereinafter. In accordance with the well known 1, 2, 4, 8 system of binary notation, the pulses on lines bl, b2, b4 and 198 during each cycle of four time periods represent the digits 1, 2, 4, and 8.

The input lines bl, b2, b4 and b8 are connected through germanium crystal diodes I0 with keyboard digit switches icl-ICS, each line being conn nected with those switches that are representative of digits associated with the pulses on the line. For example, line bl is connected with the l switch kl, and lines bl, b2 and b4 are connected with the 7 switch kl.

Switches icl-Ica are connected with a common output line Il to which a source of negative potential, say 20 volts is applied through a resistor l2 which may be of the magnitude of 100,000 ohms.

The operation of the device is as follows:

Normally the switches kl-k are open and the output line l I is at the low potential of -20 volts. Closure of a key icl-R9 connects the output line Il with one or more of the input lines through the associated diodes I0, but no change in the potential of the output line is effected until the occurrence of the digital pulses on said line or lines. The said pulses cause the diodes to conduct and the potential of the output line is raised to approximately 0 volts due to current ow in resistor l2. It is readily apparent, therefore, that the input pulses effect the generation of output pulses of the same relative timing. For example, assuming that the 5 switch lc5 is closed and connects input lines lbl and `2:-4 with the output line Il, the occurrence of a pulse on line bl during the first time period of a cycle effects the generation of an output pulse on line ll during said first time period (Figs. 2 and 3), and the occurrence of a pulse on line be during the third time period, effects the generation of a second pulse on line I I during said third period. No input pulses occur on lines bl and b4 during the second and fourth time periods and output line I l is maintained at a low potential during these periods by resistor I2.

It will be seen, therefore, that operation of the switches lai-169 translates a four line code into a single line code by transferring the timed code pulses from input lines b I, b2, b4 and bil onto out;

put line II without disturbing their relative timing.

Referring now to Figs. 4, 5 and 6, the means of the invention may operate in the described manner to emit a non-repeated digital signal under control of a single train of timed input pulses; or a speciiic predetermined number of pulses may be emitted under control of a like number of trains of input pulses. switch Ici-Ici transmits over output line I I only a predetermined number of sets of pulses representative of the digit associated with the switch, regardless of the length ofL time that the switch is maintained closed. This, arrangement is eX- tremely useful in computer input systems. Any desired means may be provided for effecting the transmission of a desired number of pulses over each input line bl, b2, be and o8 for each closure of a switch ICI-kil, but the arrangement shown in Fig. 4 is a preferred one which serves also to eliminate the undesirable effects of switch or key chatter.

Referring to Fig. 4 the output line H is cona nected through a resistor I3 which may be of the magnitude of 68,000 ohms, with a -100 volt source. Normally, therefore, output line Ii is at the low potential of 10GY volts as indicated in Fig. 6. Line II is also wired to the grid of a cathode follower connected tube It, whose cathode is connected through a resistor E5 to the 10G volt source. A condenser I6 is connected across resistor i5 and the two are so proportioned as to provide a relatively slow time constant. Thus, the potential of output line Il from said cathode is slow'in following negative excursions of the grid of the tube. Values of 130,900 ohms and .l microfarad have been found acceptable for resistor I5 and condenser l respectively. Output line Il' feeds into a differentiating networl: i3 which be of any ordinary configuration which produces sharp'positive pulses proportional in magnitude to the positive excursions of output line Il of the oathode follower. These sharp pulses control a second cathode follower it. Preferably, the grid of tube IS is biased vvolts below its cathode so that potential rises of the grid must exceed 20 volts in order to' produce an appreciable pulse on output line 2@ of the tube.

|The operation of the circuit is as follows.

Normally, digit Voutput line Il and, therefore, the output line il of the cathode follower li are at a potential of 100 Volts. Closure of a switch Fri-Jet, however, connects saidlne Ii with one or more of the input lines bI, b2, bil and t28 which are at a potential of -20 volts, and the potential thereof and of the grid of cathode follower I is raised to -20 volts. Through cathode follower action, this 8O volt rise is reflected on output line il" and a sharp pulse is produced on line 2o by differentiator I8 and cathode follower It. This pulse cn line 2i] is fed into, and initiates an operation of a pulse generator 2i which, in the present instance, is adapted to produce, on each initia- Thus the closure of any i ltion thereof, four successive pulses for transmission over lines bl, b2, bd and b3 in the proper se quence. When it is desired to transmit more than one pulse over each input line DI b2, bt and D3, the generator is arranged to do so under con trol of a single initiating pulse. Generator 2l may be of any suitable kind but preferably includes an initiator tube which is biased beyond 'cutoff by an amount which can be overcome only by a large pulse on line 2d, that is, one proportional to the volt rise on line Il. The reason l for this will become apparent hereinafter.

The four pulses emitted by generator ZI, in the present instance, serve in the same manner as described above to raise the digit output line I I to 0 volt potential and thus to display on said line the pulse representation of the digit associated with the closed switch Ici-It. The rise in potential of output line II from 20 volts to 0 volts due to the occurrence of a pulse on the appropriate line bl, b2, b4 and E8 effects, through cathode follower action, a similar rise in the potential of output line I7 of the cathode follower. Due to the rise of line I'I, the differentiator I3 produces another sharp pulse, which, however, has a maximum magnitude of only 20 volts which is not sufficient to cause cathode follower I9 to proluce an appreciable pulse on. output lne'ii. Immediately following an effective pulse on one of the lines bl, b2, bfi or b3, the'digit output line il drops to a potential of -20 volts and the output line il of cathode follower ld attempts to follow it. However, the time constant provided by resistor I5 and condenser I6 slows up the rate of potential drop of line I 'I so that an appreciable time elapses before line I'IA does reach the 20 volt level. If line Il is again raised to 0 volt potential by a second pulse, as, for example, when the 5 switch R5 is closed the just above described action is repeated and a second ineffective pulse is produced on line Il.

When a closed switch .M -7c3 is opened, some chattering occurs, and contact is made and broken one or' more 'times before being broken cleanly. This chattering' effects a' momentary fluctuation of the potential of digit output line I between -20 volts and 10U volts, that is, the closed and open switch conditions. These fluctuations are reflected on the grid of tube le, but the time constant of resistorV i5 and con-denser I6 `prevents the immediate lowering of the p0- tential of line I'I .to *100 volts so that the upward uctuations thereof'to 20 volts are of small magnitude and only small ineifective'pulses, if any, are produced on line 2c by d'nerentiator i8 and cathode follower I9. When the switch chatter terminates and the potential of line I i comes to rest at volts, the potential of line i7 fol lows under control :of its timeconstant. It is believed apparent that-if the potential of line il ywere allowed to fall to a potential of lilo volts immediately after a switch icl- Mis closed, the fluctuations thereof rdue to switch chatter would allow differentiator I8 to produce pulses of sufficient magnitude to trigger generator 2l again. This, of course, Awould result in a misoperation 'of the device.

ylt is to be mentioned that in choosing the values of resistor I5 Iand condenser it, a coinpromise is made `between a slow time constant and high keying speed, that is, the time required between the opening of one switch Ici-Jog and the closure of another for line il to reach a potential that is suiiiciently negative to assure an operation of generator 2l as ya result of said closure. Further, it is to be understood that Ithe potential levels of 0, and -100 volts, and the disclosed values of the several circuit compnents are only by way of example and that any other suitable values may be substituted therefor without departing from the spirit of 'the invention. Also, whereas the invention has been applied to the translation of a four line code into a single line code, it is equally Well adapted for the translation of yany plural line code into a single line code.

While there has been described what is considered to be a highly desirable embodiment oi the invention, it is obvious that many changes in form could be made Without departing from the spirit of the invention, and no limitation is made to the exact form herein shown and de scribed, nor to anything less than the whole of the invention as hereinbcfore set forth, and as hereinafter claimed.

I claim:

1. A translating circuit comprising an outpu-t line, a resistor connecting said line with .a source of potential, a plurality of input lines lat a much higher potential than said output line, a series of diodes inserted between said input lines and said output line and made conducting by said diiference in potential, a series of keyboard switches, one for each signal to be transmitted and each connected in series with one or more of said diodes between said output l-ine and one or more of said input lines, a cathode follower having its grid connected to said output line, a differentiating network fed by said cathode follower, :and a pulse generator adapted to produce a predetermined number of pulses for transmittal over said input lines, tripped by a pulse from the difierlentiator.

2. A translating circuit comprising an output line, a resistor connecting said line with a source of potential, a plurality of input lines at a much higher potential than said output line, a series of diodes inserted between said input lines and said output line vand made conducting by said difference in potential, a series of keyboard switches, one for each signal .to be transmitted and each connected in series with lone or more of said diodes between said output line and one or more of said input lines, `closure of la said switch raising the output line to the much higher potential of the input lines, a cathode follow-er having its grid connected to said output line, a diierentiating network fed by said cathode follower and emitting Ia large pulse on closure of a said switch, and a pulse generator adapted to produce a predetermined number of pulses for transmittal over said input lines, tripped by said large pulse from the diierentia-tor, one or more of said input line pulses raising the potential of the output line a smaller amount to provide output pulses, and said smaller -amount also producing a diiferentiator output pulse of insuflicient magnitude to trigger said generator.

3. A translating circuit comprising an output line, a resistor connecting said line with a source of potential, a plurality of input lines at a much higher potential than said output line, a series of diodes inserted between said input lines and said output line and made conducting by said difference in potential, a series of keyboard switches, one for each signal to be transmitted and each connected in series with one or more of said diodes between said output line and one or more of said input lines, closure of a said switch raising the output line to the much higher potential of the input lines, a cathode follower having its grid connected to said output line, a diilerentiating network fed by said cathode follower and emitting a large pulse on closure of a said switch, a pulse generator adapted to produce a predetermined number of pulses for transmittal over said input lines, tripped by said large pulse from the differentiator, one or more of said input line pulses raising the potential of the output line a smaller amount to provide output pulses and said smaller potential rise also producing a diiferentiator output pulse of insufficient magnitude to trigger said generator, and an RC network between said cathode follower and said dierentiator to slow the negative swing of the differentiator input when a said switch is opened and thus prevent large positive swings thereof due to make and break switch chatter.

4. A translating circuit comprising an output line, a resistor connecting said line with a source of potential, a plurality of input lines at a much higher potential than said output line, a series of diodes inserted between said input lines and said output line and made conducting by said difference in potential, a series of keyboard switches, one for each signal to be transmitted and each connected in series with one or more of said diodes between said output line and one or more of said input lines, closure of a said switch raising the output line to the much higher potential of the input lines, a cathode follower having its grid connected to said output line, a differentiating network fed by said cathode follower and emitting a large pulse on closure of a said switch, a pulse generator adapted to produce a predetermined number of pulses for transmittal over said input lines, tripped by said large pulse from the diiferentiator, one or more of said input line pulses rasiing the potential of the output line a smaller amount to provide output pulses and said smaller potential rise also producing a diiferentiator output pulse of insuii'- cient magnitude to trigger said generator, and an RC network associated with the cathode of said follower to slow the negative swing of said cathode when a said switch is opened and prevent large positive swings thereof due to make and break switch chatter.

WILLIAM HENRY BURKHART. HOWARD M. FLEMING, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Proceedings of the IRE, February 194s, pages 139-147, pages 143-144 in particular (Rectiiier Networks for Multiposition Switching by Brown and Rochester) 

